Apparatus for indicating the characteristic data of a centrifuge

ABSTRACT

An apparatus is disclosed for providing a digital indication of characteristic data measurements of a centrifuge centrifugal head for examining the contents of test vessels, characterized by an indicator capable of showing directly, according to the adjustment of a selector switch, the acceleration, number of revolutions per unit of time and rotor characteristic data.

This invention relates to improvements in apparatus for indicating thecharacteristic data of a centrifuge.

The invention relates to an apparatus for the digital indication ofcharacteristic data of a centrifuge centrifugal head for examining thecontents of test vessels, namely the number of revolutions per unit oftime of the centrifugal head and the acceleration of the rotorcharacteristic datum acting on the centrifuged material.

A laboratory centrifuge is already known having a device with which thenumber of revolutions as well as the different accelerations can bemeasured. How this device operates is not known.

The invention is based on the use of an apparatus with which, in asimple manner and for laboratory examinations, a sufficiently accurateas well as relatively rapid an indication of the characteristic data ofinterest of a centrifuge when centrifuging is obtained.

According to the invention an input for the maximum radius ofcentrifuging and an input for the minimum radius of centrifuging of thecentrifuge head arrangement are provided, both inputs being connected toan electronic constructional element having an output for the numbers ofrotations, the acceleration and the rotor characteristic data, andconnected via a selector switch to an indicator.

According to the adjustment of the selector switch the indicator showsdirectly one of the three given characteristic data and is of interestin the centrifuging procedure. Hitherto only the two inputs which willbe explained more precisely hereinafter had to be adjusted and in factindependently of the respective characteristic data to be read and theselector switch must be adjusted to one of the three outputs. Theelectronic unit translates the values given to it automatically intovalues which deliver via the respective connected output the respectiveresults.

The invention is explained in more detail with reference to oneembodiment from which further important features follow:

FIG. 1 shows diagrammatically a circuit diagram of an apparatusaccording to the invention;

FIG. 2 shows a section through a centrifugal head with an inserted testvessel.

An input 1 for the maximum radius of centrifuging is connected via alead 2 to an electronic constructional element 3. A further input 4 forthe minimum radius of centrifuging is connected via a further lead 5 toan input of the constructional element 3.

The constructional element has three outputs 6, 7, and 8. A selectorswitch 9 connects a lead 10 selectively to one of the outputs 6, 7, or8. The lead 10 is connected to a digital indicator 11.

The input 1 and the input 4 may be manually adjusted by means of threedigit counters for the adjustment of the maximum radius of centrifugingand of the minimum radius of centrifuging. Both magnitudes can be seenfrom the attached FIG. 2 which shows a section through a centrifuge headwith a test vessel 13 mounted in a suspension 12. The axis of rotationof the centrifuge head is indicated by reference 14. Thus the maximumradius of centrifuging is equal to the distance of the axis of rotationfrom the bottom of the test vessel 13. The minimum radius ofcentrifuging depends on the actual quantity in the vessel.

In FIG. 2 the middle centrifugal radius r_(m) and the suspension radiusr_(er) as well as the radius of the working head r_(ak) are indicated.With the exception of the middle centrifugal radius and the minimumcentrifugal radius, the other radii of FIG. 2 are supplied to thecustomer by means of data sheets in dependence on different magnitudesof the measurement for suspension and test vessels.

The number of revolutions n per minute is measured directly via a speedgenerator, (not shown), which is fixed on the motor of the centrifuge.For indicating the number of revolutions the key "number of revolutions"(not shown) is pressed so that the selector switch 9 is set on theoutput 6. The notification of the actual numbers of revolutions is thenshown on the indicator 11 directly numerically by the six digit figures.

As regards the acceleration, the maximum acceleration and the minimumacceleration are measured. For measuring the maximum acceleration themaximum centrifugal radius r_(max) is adjusted by the respective tableand in fact on the input 1.

Furthermore the minimum centrifugal radius r_(min) is set at zero. Thekey "Acceleration" is then pressed and the indication is effectedimmediately.

For indication of the minimum acceleration r_(min) is set on the input 4and in fact independently of the actual or otherwise known fillingquantity to be measured or r_(min) must be measured as a defineddistance in FIG. 2.

Furthermore r_(max) is set to zero. The key "Acceleration" is thenpressed whereby again the selector switch 9 is connected to the output 7and the indication is shown directly on the indicator 11.

Finally the k value can be selectively measured which is a measurementfor the separation action of a laboratory centrifuge. A rotor is all themore effective the smaller the k value. Furthermore with knowledge ofthe k value and material related sedimentation constant 2 theprecipitation time of the centrifugal material can be calculated in asimple manner. For measuring the k value r_(max) is adjusted and r_(min)is adjusted. Finally the key, "k value" (not shown) is pressed toconnect the selector switch 9 to the output 8 and the indication isshown at the indicator 11.

The apparatus shown may, of course, also be varied so that furthercharacteristic data of interest can be obtained and indicated from thedescribed measurements measured or only one or two of the threemeasurements shown are measured and indicated.

For explaining the manner of operation of the constructional element 3the following consideration is set forth.

With the aid of the formula ##EQU1## the multiples of the normalacceleration achievable with a centrifuge can be calculated. RZB is thusthe relative centrifugal acceleration. The equation RZB = ZB/_(gn)gives, as ZB = r.W² (W = angular speed in 1/S) ans W = 2 . π . n and nis given in revolutions per min (1 min = 60^(s)) s = seconds ##EQU2##

By shortening of the units and distribution of constants and variablesone then arrives at ##EQU3## which gives ##EQU4## whereby according todefinition r is inserted in mm and n in min⁻¹.

The k value is derived as follows:

From the formula ##EQU5## these follow: ##EQU6##

Radius r_(max) and r_(min) must be adjustable manually up to max 500 mm,1,118 . 10⁻⁶ and 2.533 . 10¹¹ are constant factors.

The number of revolutions appears in both equations squared.

With the k value the precipitation time is calculated according to thefollowing numerical value equation:

t_(N) = k s

t_(N) = precipitation time in h

k = rotor characteristic data measurement in h

S = Svedberg number

S is also indicated as the sedimentation constant. It indicates thesedimentation properties of the particules to be centrifuged.

The constructional element 3 therefore in the manner stated effects theconversion from its inputs to the respective output.

What is claimed is:
 1. An apparatus for the digital indication of data measurements of a centrifuge centrifugal head for the examination of the contents of test vessels, specifically the number of revolutions per minute of the centrifugal head, the acceleration acting on the centrifugal material and/or the rotor characteristic data comprising a measuring device to measure the speed of the centrifuge motor, an imput for the maximum centrifugal radius and an imput for the minimum centrifugal radius of the centrifugal head, said inputs being connected to an electronic constructional element containing outputs for each of the number of rotations, the acceleration and the rotor characteristics data, each output connected by means of a selector switch to an indicator. 